Sexual Development in Phytophthora

本研究将以植物病原菌疫霉属（Phytophthora）为模型，阐明卵菌真菌交配和性孢子发育的发育生物学和遗传学。卵菌是一种重要的但尚未得到充分研究的低等真核生物，包括许多具有经济和环境意义的动植物病原体，其他病原体的生物防治剂和腐生植物。卵菌和其他微生物一样，交配是生命周期的重要组成部分。交配会形成卵孢子，这是一种耐用的结构，可以在季节之间存活下来，从而引发疾病流行。性循环还使基因在种群中流动，产生更适合的菌株，这是由于决定致病性、寄主偏好、杀菌剂抗性和其他性状的基因座的新组合。该提案的大部分内容都集中在病原菌上，这是一种毁灭性的植物病原体（马铃薯晚疫病），每年造成数十亿美元的损失。它也是研究卵菌生物学的一个很好的模型系统。病原菌是异源性的，当不同交配类型的分离物通过激素相互作用时，通常会诱导卵孢子。在之前的工作中，鉴定了9个在交配过程中诱导的基因。在这个项目中，将采用多学科的方法来解决这些交配调节基因的功能和调节。这将需要识别额外的调控基因，并研究基因的一部分结构，其蛋白质产物的细胞定位，以及沉默和强制表达的影响。除了研究病原菌外，基因的表达也将在同源物种P. phaseoli中进行表征，该物种在单次培养中产生卵孢子。还将对交配过程中分泌的新化学物质进行初步研究。这项调查的结果将产生概念上和实际上的影响。更好地理解用于指导真核细胞分化，应对压力和形成生存结构的各种策略。发展中的重要问题将被解决，如细胞通讯，自我/非自我识别，细胞类型确定，基因调控和信号转导。同质和异质交配系统的基础也将被阐明。与子囊菌和担子菌等其他低等真核生物相比，卵菌的交配受到的调节可能不同，因为子囊菌和担子菌在分类上与卵菌缺乏亲缘关系。从长远来看，如果能够确定控制交配的因素，就有可能通过使用合理的基于机制的抑制剂而不是对环境有害的化学品来操纵病原体的生命周期来控制植物疾病。

This research will elucidate the developmental biology and genetics of mating and sexual spore development in oomycete fungi, using the plant pathogenic genus Phytophthora as a model. Oomycetes are an important but understudied group of lower eukaryotes that include many economically and environmentally significant pathogens of plants and animals, biocontrol agents of other pathogens, and saprophytes. In oomycetes as in many other microbes, mating is an important element of the life cycle. Mating results in the formation of oospores, which are durable structures that can survive season-to-season to initiate disease epidemics. The sexual cycle also enables gene flow through populations, yielding strains that may be more fit due to new combinations of loci determining pathogenicity, host preference, fungicide resistance, and other traits. Much of this proposal focuses on P. infestans, which is a devastating plant pathogen (potato late blight) that causes many billions of dollars of damage per year. It is also a good model system for studying oomycete biology. P. infestans is heterothallic, and oospores are normally induced when isolates of different mating types interact through hormones. In previous work, nine genes induced during mating were identified. In this project a multidisciplinary approach will be used to address the function and regulation of such mating-regulated genes. This will entail identifying additional regulated genes, and for a subset of the genes studying their structure, cellular localization of their protein products, and the effects of silencing and forced expression. In addition to studies of P. infestans, the expression of the genes will also be characterized in a homothallic species, P. phaseoli, which produces oospores in single culture. Preliminary studies of novel chemicals secreted during mating will also be performed. Results from this investigation will have conceptual as well as practical impacts. A better understanding will be obtained of the diverse strategies used to direct eukaryotic cell differentiation, to respond to stress, and to form survival structures. Important issues in development will be addressed such as cellular communication, self/nonself recognition, cell type determination, gene regulation, and signal transduction. The basis of homothallic and heterothallic mating systems will also be illuminated. It is likely that mating in oomycetes is regulated differently than in other lower eukaryotes such as ascomycetes and basidiomycetes, which lack taxonomic affinity to oomycetes. In the long term, if the factors which control mating can be identified, it might be possible to control plant diseases by manipulating the life cycles of pathogens using rational mechanism-based inhibitors instead of environmentally harmful chemicals.